Grommets that are insertable through a hole in panel are well known. Such grommets typically include an opening therethrough to allow passage of a body, for example a wire or wiring harness, through the grommet, and consequently through the panel. It may be desirable to minimize the force required, i.e. insertion force, to insert the grommet through the hole of the panel. At the same time, it is also may also be desirable to maintain a force required to remove the grommet from the hole, i.e. pull-out force, which may typically be substantially higher than the insertion force to securely retain the grommet within the hole after installation. In one example, a maximum insertion force of 40N may be desired while minimum a pull-out force of 100N may be desired. More generally it may be desirable for the grommet to have pull-out force that is at least 1.5 times the insertion force.
One way to decrease the insertion force of the grommet is to apply a lubricant to the exterior surface thereof to reduce friction between the exterior surface of the grommet and the hole of the panel. While this method may be effective, the lubricant may be messy or may not be compatible with insulation used on the wire which passes through the grommet. Some lubricants may not provide the desired benefit because they may dissipate too quickly to be beneficial.
Another way to decrease the insertion force of the grommet is by the design or geometry of the grommet. In one design to decrease insertion force, thick ribs may be placed on the outside surface of the grommet which contacts the hole during insertion of the grommet. This creates localized points of contact, which in turn leads to less friction during insertion of the grommet. However, the thick ribs add material and therefore mass and cost to the grommet.
In another design, shown in US Patent Application Publication No. 2005/0139381, a series of relief grooves are placed on the internal surface of the grommet. These relief grooves extend to the end of the grommet and are so placed to decrease the insertion force of the grommet. However, the nature of the relief grooves allows the relief grooves to contract during insertion of the grommet, thereby minimizing the benefit of the relief grooves.
What is needed is a grommet which minimizes or eliminates one or more of the shortcomings as set forth above, what is also needed is such a grommet which reduces the insertion force of the grommet.